Means for and method of preventing failure of refrigerator operation



April 21, 1959 zw c 2,882,695

MEANS FOR AND METHOD OF PREVENTING FAILURE 0F REFRIGERATOR OPERATION Filed Dec. 13, 1954 I 2 Sheets-Sheet 1 IN V EN TOR.

' BY j g mw United States Patent MEANS FOR AND METHOD OF PREVENTING FAILURE OF REFRIGERATOR OPERATION Joseph Zwickl, Chicago, 11]., assignor to Refrigeration Appliances, Inc., Chicago, 11]., a corporation of Illinois Application December 13, 1954, Serial No. 474,865

7 Claims. (Cl. 62-119) This invention relates to refrigerating systems wherein an evaporable refrigerant is circulated through a closed system in a portion of which the refrigerant is compressed and liquefied and in another portion of which the thus compressed and liquefied refrigerant is evaporated to abstract heat and thereby accomplish the refrigerating purpose, the invention having reference more particularly to means for and a method of insuring refrigerator operation at times of abnormal low pressure of the liquefied refrigerant.

In such systems a refrigerant is circulated by a compressor through the system and converted in the high pressure side into a liquid which is supplied through an expansion valve to the low pressure side in which it is evaporated to perform the refrigerating or coo-ling function, after which the thus evaporated refrigerant is returned by the compressor to the high pressure side for reconversion to a liquid and reuse.

The liquid refrigerant is supplied to the expansion valve through a shut off valve which is operated at such intervals as are required to maintain the desired refrigerating or cooling eifect, and the operation of the compressor is controlled by the pressure in the low side of the system so that it operates during evaporation of liquid refrigerant and ceases operation when the supply of liquid refrigerant is interrupted to the low pressure side and the latter side has been pumped down to a sufiiciently' high degree of evacuation to insure evaporation as soon as liquid refrigerant is again supplied to the low pressure side.

The liquid refrigerant is pressed through the expansion valve by pressure in the high side of the system which under normal operating conditions is ample for the purpose, but it sometimes occurs that the pressure in the high pressure side of the system falls below that required for operation of the expansion valve, and by reason thereof the refrigerating system is incapable of operating when and as required. The principal object of the present invention is to insure a supply of liquid refrigerant to the evaporator at such times when the pressure in the high pressure side of the refrigerating system is insufficient to supply liquid refrigerant through the expansion valve, as aforesaid, and thereby avoid failure of refrigerator operation.

Other objects of the invention are, to provide means for and a method of accomplishing the above indicated purpose of the invention which are reliable and readily applicable to such refrigerating systems; to effect the supply of'liquid refrigerant at the above indicated times through facilities which are auxiliary to and do not afiect or interfere with the normal operation of the system; to control the operation of these facilities by the pressure in the high pressure side of the system so that they function with certainty when required; and to permit the invention to be incorporated in existing systems without substantial change or alteration thereof, all of these and other objects being accomplished as pointed out more particularly hereinafter and as shown in the accompanying drawings, in which:

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Fig. 1- is a view which is somewhat diagrammatic and shows a refrigerating system having a pressure booster incorporated therein in accordance with the present invention;

Fig. 2 is an enlarged vertical sectional view of the pressure booster of Fig. 1; and

Fig. 3 is a view, similar to Fig. 2, showing a modified form of pressure booster.

In the drawing the invention is shown in a preferred form in connection with a refrigerating system of conventional type, and the various conventional parts of the refrigerating system are shown somewhat diagrammatically and are not explained in detail as these parts, and the construction and operation thereof, are. well known and various types thereof are commonly used and available on the market.

Also it is to be understood that this conventional refrigerating system is shown in simplified form and that in practice it may include other and different parts and that the invention is not limited to such simplified system but may be employed in other and more elaborate refrigerating systems in which conditions may occur by reason of which the invention is useful therein.

Referring particularly to Fig. 1 of the drawings, the reference numeral 10 indicates an enclosure, parts of which are broken away, of a compartment 11 which is to be refrigerated or cooled, and this compartment contains a heat exchanger 12, commonly known and referred to hereinafter as the evaporator, which has at the inlet end thereof an expansion valve 13 through which liquidrefrigerant is supplied to the evaporator 12 for evaporation therein to extract heat fro-m the compartment 11. This expansion valve 13 is controlled by a bulb 14 which is located at or near the outlet fro-m the evaporator at a place where it is responsive to the temperature of the refrigerant leaving the evaporator so as to regulate the supply of liquid refrigerant to the evaporator according to the completeness of evaporation occurring in the evaporator.

The evaporator outlet is connected by a pipe or tube 15 hereinafter referred to as the suction line, to the intake of a compressor 16 which is operable by a motor 17 to evacuate evaporated refrigerant from the evaporator 12 and maintain in the evaporator a condition of evacuation which will insure evaporation of liquid refrigerant in the evaporator 12 as such liquid refrigerant is supplied thereto through the expansion valve 13.

The evaporator 12 and suction line 15 constitute the portion of the refrigerating system which is commonly known as and will be referred to hereinafter as the low pressure side of the system.

The compressor 16 compresses the vaporized refrigerant as it is evacuated from the evaporator 12 as aforesaid and discharges the thus compressed refrigerant into a pipe or tube 18, hereinafter referred to as the discharge line, which leads to the inlet of a heat exchanger 19, commonly known and referred to hereinafter as the condenser, which is located at a place where it is exposed to cooling conditions, for example at the exterior of the building above the roof 20 as shown herein, and the outlet of this condenser is connected by a pipe or tube 21 to a receiver 22in which a supply of liquid refrigerant is maintained in readiness to perform its refrigerating function. g

A pipe or tube 23, hereinafter referred to as the refrigerant supply line, leads from the receiver 22 to a shut off valve 24 and from the shut off valve to the expansion valve 13, as indicated at 25, and in accordance with the present invention a check valve 26 and a booster 27 are interposed in the refrigerant supply line 23, preferably at a place near the shut off valve and arranged so that the liquid refrigerant supplied to the shut off valve j 2,882,695. a f

passes through the check valve 26 and therefrom into the a booster 27 and from the booster to the shut ofli valve 24.

The booster 27 may be of any form and construction sultable to accomplish the hereinafter explained purpose thereof, a preferred form thereof being shown in Fig. 2 comprises a closed container 28 having a chamber 29 therein with an inlet pipe 30 extending upwardly therein nearly to the top of the chamber as shown in Fig. 2. This pipe 30 18 open at the top and at itslower end extends through the bottom of the container, being sealed thereto at this place, and its projecting lower end is connected to the check valve 26 which is arranged so that the valve 31 thereof opens in the direction to permit flow of refrigerant liquid through the check valve 26 to the charn- 'ber 29 of the container and closes to prevent fiow thereof in the reverse direction from the chamber 29.

An outlet pipe 32 extends downwardly in the chamber 29 nearly to the bottom thereof as shown in Fig. 2, .and

'is open at the lower end and at its upper end, this pipe 32 extends through the top of the container, being sealed thereto at this place, and its projecting upper end is connected to the shut off valve 24 as shown in Fig. 2.

A small bleeder opening 33 is provided in the pipe 32,

at the upper end thereof within the chamber 29.

For reasons explained hereinafter the container 28 is surrounded by a heater coil 34 and enclosed in heat insulation 35.

The various parts above described through which the refrigerant is conducted from the compressor 16 to the expansion valve 13 constitute the portion of the refrigerating system which is commonly known as and will be referred to hereinafter as the high pressure side of the system, and in and throughout this high pressure side a sufficiently high pressure is maintained by the compressor to convert to a liquid the evaporated refrigerant which is evacuated from the low pressure side of the system and transferred by the compressor to the high pressure side of the system. The evacuated vaporized refrigerant is not converted immediately to a liquid upon compression and discharge thereof into the high pressure side of the system as the refrigerant is heated by the compression thereof and re- .mains in the form of a gas in the high pressure side until ,sufiicient heat is dissipated therefrom by circulation therelot in the condenser 19 for condensation thereof to a liquid at the pressure maintained in the high pressure side of 'the system.

Thus the refrigerant exists in the initial portion of the high pressure side as a gas and before it reaches th receiver 22 it is converted into a liquid.

The booster 27 is near the terminal end of that portion of the high pressure system which is filled with liquid refrigerant and is capable of and generally is filled, except at times hereinafter explained, to a high level with liquid refrigerant at least as high as the bleeder orifice 33.

The refrigerating system is operated periodically to .maintain the desired temperature in the compartment 11 vided with a solenoid 36 by which it is opened, is controlled by a thermostat 37 which is located in the compartment 11 at a place to be responsive to the temperature prevailing in the compartment.

This thermostat 37 is adjustable, as for example by a knob 38, so that it may be set at any selected low tem- 'perature which it is desired to be maintained in the compartment 11, and is arranged so that when the temperature in the compartment rises above the temperature at which the thermostat 37 is set it closes an electrical circuit 39, 40 which thereupon supplies current to and energizes the solenoid 36 and thereby opens the shut off valve 24. Low voltage current is preferably employed 4 for this circuit and provided in a manner hereinafter explained.

Opening of the shut off valve 24 permits liquid refrigerant to be supplied from the receiver 22 to and through the expansion valve 13 to the evaporator 12 for evaporation therein to cool the compartment 11, and when such evaporation has continued until the temperature in the compartment is below the temperature at which the thermostat 37 is set the thermostat 37 thereupon operates to open the circuit 39, 40 to the solenoid 36 and the shut off valve 24 thereupon closes and remains closed until the temperature in the compartment 11 is again above that at which the thermostat 37 isset.

Inasmuch as evaporation of the liquid refrigerant in the evaporator 12 depends upon maintenance of a sufliciently low pressure in the low pressure side of the system and it is a function of the compressor to maintain such low pressure therein, it is customary to control the operation of the compressor 16 by the pressure in the low side ofthe system so that the compressor will operate when and as long as operation thereof is necessary for this purpose.

The motor 17 which operates the compressor 16 is connected by conductors 41, 42 to current supply mains 43, 44 to which current is supplied from a suitable source of current through a main switch 45, and a switch 46 is interposed in the circuit from the supply mains 43, 44 to the motor, for example in the conductor 42, to control the operation of the motor 17. This switch 46 is operable by a pressure responsive element 47 which is connected to the suction line 15 of the low pressure side of the system, as indicated at 48, so that the pressure responsive element 47 responds to the pressure in the low pressure supplied thereto and to evacuate the vapor or gas from said low pressure side as it is created therein by such evaporation and thereby maintain the required low pressure for such evaporation, and accordingly the pressure responsive element 47 is arranged so that the switch 46 is opened and remains open only when the pressure in the low pressure side of the system is less than a predetermined low pressure necessary for proper evaporation, and the pressure responsive element 47 is arranged to close the switch 46 and retain said switch in the closed position at all other times.

Thus the operation of the refrigerating system is controlled by the shut off valve 24 and the operation of the compressor 16 is indirectly controlled by the operation of said shut off valve through the condition which exists in the low pressure side of the system due to the opening and closing of said shut off valve.

By reason thereof, when the shut off valve 24 is closed, the operation of the compressor is continued until the low pressure side of the system is pumped down or evacuated to a pressure below the aforesaid predetermined low pressure, whereupon the pressure responsive element 47 then opens the switch 46 and the operation of the compressor 16 is discontinued.

When, on the other hand, the shut off valve' 24 is opened and liquid refrigerant thus suppliable to the expansion valve 13 and through the latter to the evaporator 12, the evaporation of the liquid refrigerant in the evaporator releases vapor or gas which causes increase in pressure in the low pressure side above that at which the expansion element 47 maintains the switch 46 in the open position and this increase in pressure thus resulting from the restoration of supply of liquid refrigerant to the evaporator causes operation of the pressure responsive element 47 to close the switch 46 and thus. cause Thus the refrigerating system is intermittently operable to supply liquid refrigerant to the evaporator 12 as required to maintain the temperature in the compartment 11 at the temperature at which the thermostat 37 is set.

The heating coil 34 of the booster 27 is connected to the current supply conductors 43, 44 through a switch 49 to energize the heating coil and heat the contents of the booster compartment 29 at selected times, and this switch 49, which is normally open, is closable by a solenoid 50 which is connected through conductors 51 and 52 with the conductors 39 and 40 of the low voltage circuit which is controlled by the thermostat 37 and thus the solenoid 50 is operable to close the switch 49 only when the thermostat 37 closes the circuit to the solenoid 36 and the shut off valve 24 is opened.

Current may be supplied to the circuit 39, 40 at the desired low voltage from the current supply mains 43, 44 through a transformer 53 if the current supplied to the mains 43, 44 is alternating.

The energization of the solenoid 50 to close the switch 49 not only is controlled by the thermostat 37 in the compartment 11, but is further controlled by a switch 54 which is operable by a pressure responsive element 55 which is connected as indicated at 56 to the liquid refrigerant supply line 23 at a place ahead of the check valve 26 as shown in Fig. 1, the arrangement being such that the switch 54 is held in the open position by the pressure responsive element 55 as long as pressure is maintained in the supply line 23 ahead of the check valve 26 above a predetermined level but when the pressure in said supply line 23 ahead of the check valve 26 falls below that predetermined level the pressure operable element is operated to close the switch 54 and retain the switch 54 in the closed position as long as the pressure in the supply line 23 ahead of the check valve 26 remains below that predetermined level.

The expansion valve 13 is of conventional type having an opening, variable by the temperature of the bulb 14, through which the amount of liquid refrigerant required for operation of the evaporator 12 is forced by the higher pressure normally maintained in the high pressure: side for evaporation of the liquid refrigerant in the evaporator, and accordingly it is essential for operation of the system that the liquid refrigerant be supplied to the expansion valve 13 at a higher pressure than that existing in the evaporator 12.

Generally such refrigerating systems are designed so that sufiicient pressure is maintained in the high pressure side to force liquid through the expansion valve whenever required, but it sometimes occurs that the pressure in the high pressure side of the system may, because of abnormal conditions, fall below that required to press liquid refrigerant through the expansion valve 13, in which event the refrigerating system fails to operate.

For example, when the condenser 19 is located at the outside of the building as shown herein, the temperature of the contents of the high pressure side of the system may, at times of extremely low outside temperature, be reduced to such an extent during a prolonged period when the compressor 16 is inoperative, that when the thermostat 37 closes the circuit 39, 40 and opens the shut off valve 24, liquid refrigerant is not supplied through the expansion valve 13 to the evaporator 12, and as such supply is then necessary in order to increase the pressure in the low pressure side of the system sufficiently to cause operation of the switch 46 to start the motor 17 the refrigerating system fails to function. g

In the illustrated structure, the pressure responsive element 55 is connected to the liquid refrigerant supply line 23 ahead of the check valve 26, as aforesaid, so that the element 55 is responsive to the reduction. of pressure caused in the high pressure side of the system by such above. mentioned abnormal conditions, and in accordance with the present invention the pressure responsive element 55 is arranged so that as long as the pressure existing in the high pressure side of the system is sufficient to supply liquid refrigerant through the expansion valve 13 the switch 54 is open and remains open, but when the pressure in the high pressure side of the system falls below that required to supply liquid refrigerant through the expansion valve the switch 54 is closed and remains closed as long as such low pressure condition continues in the high pressure side of the system. 1

When this switch 54 is thus closed, current is suppliable therethrough from the circuit 39, 40 to energize the sole noid 50 and close the switch 49 through which current is suppliable from the mains 43, 44 to energize the heating coil 34 and thus heat the contents of the booster 27, but as no current is available in the circuit 39, 40 unless and until that circuit is closed by the thermostat 37 in the compartment 11 the closing of the switch 54 does not cause energization of the heating coil 34 but merely sets up a condition whereby energization of the heating coil 34 is caused to occur when the thermostat switch 37 is closed.

The container 28 of the booster 27 is normally filled to a substantially high level with liquid refrigerant and the size and capacity of the container 28 is such that the amount of liquid refrigerant thus normally contained therein is ample for the purpose thereof hereinafter explained. By reason of the check valve 26 the contents of the booster container 28 are unaffected by any reduction of pressure in that portion of the high pressure side of the system up to the check valve 26 which may occur as a consequence of abnormal conditions as explained above, as the contents of the container 28 are isolated by the check valve 26 from the portion of the high pressure side of the system up to or ahead of the check valve.

By reason of the above explained construction, when the thermostat 37 closes the circuit 39, 40 and opens the shut off valve 24 at a time when the pressure in the high pressure side of the system is less than that required to supply liquid refrigerant through the expansion valve 13, the switch 54 will already have been closed by that lessened pressure and accordingly when the circuit 39, 40 is thus closed and the shut off valve 24 opened, the solenoid 50 is then energized to close the switch 49 and the booster heater coil is thereby energized and heats the booster and the isolated quantity of liquid refrigerant therein.

Such heating causes evaporation of liquid refrigerant to occur in the chamber 29 of the booster container 28 and the gas resulting therefrom accumulates in the top of the chamber 29, and as the bleeder opening 33 is quite small and only a negligible amount of gas escapes therethrough at the time, and as the chamber 29 is also closed off at the time from the remainder of the high pressure side of the system by the check valve 26, the thus accumulating gas in the top of the container chamber 29 creates pressure therein which forces the liquid refrigerant in the chamber 29 to flow out therefrom through the outlet pipe 32 and open shut off valve 24 to the expansion valve 13 at such pressure that it is supplied through the expansion valve to the evaporator 12 and vaporized therein, whereupon the pressure in the low pressure side of the system increases and operates the switch 46 to cause operation of the motor 17 and compressor 16.

Thereupon heated compressed gas is supplied to the high pressure side of the system which soon increases the pressure therein sufficiently to exceed the pressure temporarily created in the booster container 28 whereupon liquid refrigerant begins to and continues to flow from. the receiver 22 through the check valve into the booster container 28 at a pressure sufficiently high for normal operation of the expansion valve 13 and thus normal operation of the refrigerating system is restored.

Obviously the capacity of the booster chamber 29 must be such that the quantity of liquid refrigerant which accumulates therein during normal operation of the system is ample to insure starting of the compressor 16 and'r'esumption of normal operation of the system as aforesaid and, moreover, the heating coil 34 must be of suitable wattage capacity to heat the liquid refrigerant in the container 28 sufficiently and at a rate to produce gas in the chamber 29 substantially in excess of that which may escape through the bleeder opening 33 and to continue the accumulating gas pressure for a sufiicient length vof time and at a sufficient pressure to insure starting of the compressor and resumption of normal operation of the system.

As soon as the resumed operation of the compressor 16 builds up in the high pressure side of the system a pressure sufficiently high for normal operation of the expansion valve 13 the pressure responsive element 55 responds to that increased pressure and opens the switch :54 and thereby through the solenoid 50 and switch 49 interrupts the current supply to the heating coil 34 and this switch 54 thereafter remains open, irrespective of 'and'throughout operations of the thermostat switch 37 in the compartment 11, until another occasion of abnormal ,rfeduction of pressure in the high pressure side of the ,sy'stem. When the current supply to the heating coil 34 is interrupted as aforesaid, the booster 27 cools quite rapidly reduction of pressure in the high pressure side. Inasmuch as the check valve 26 prevents back flow of liquid refrigerant from the booster container 28 and thus serves to maintain the liquid refrigerant in the ,chamber 29, throughout normal operation of the system, ,at the high level to which it is filled as aforesaid, it is not essential that the inlet pipe 30 extend above the bottom of the container 28 and accordingly a modified form of booster may be employed, as shown in Fig. 3, if desired.

In this Fig. 3 construction the container only of the booster is shown and indicated by the reference numeral, although it is to be understood that it is surrounded by a heating coil and enclosed in heat insulating material like the container 28 of Fig. 2, and the liquid refrigerant supply pipe from the check valve 26 extends only to the bottom of the container 57, preferably at the center thereof, and is of course secured to the bottom of the container in a secure hermetically sealed manner.

The outlet pipe 58 from the container 57 leads to the shut oif valve 24 in the same manner as the outlet pipe 32 of Fig. l and this pipe 58 extends centrally through ,the top of the container 57 and is hermetically sealed .thereto and projects downwardly in the interior of the container 57 nearly to the bottom thereof and has the open lower end thereof directly above the entrance from the liquid refrigerant supply pipe from the check valve 26. This outlet pipe 58 may be flared at the lower end as indicated in Fig. 3 and of course has a bleeder opening 59 near the upper end thereof within the container 57. While I have shown and described my invention in a preferred form, I am aware that various changes and modifications may be made therein without departing from the principles of the invention, the scope of which .is to be determined by the appended claims.

What is claimed is: p 1. A refrigerating system in which a refrigerant is circulated and having a low pressure portion which includes an evaporator, an expansion valve through which liquid refrigerant is suppliable to the evaporator, and a high :pressure portion from which liquid refrigerant is suppliable to theexpansion valve and in which pressure is li firmally maintained suficiently high to force liquid refrigerantthrough the expansion valve to the evaporator, and means which is cooperable with said system, to temporarily supply liquid refrigerant to the evaporator in the absence-of said normally maintained sufficiently high pressure in said high pressure portion, said means including a compartment from which heat is extracted by the evaporator, a thermostat responsive to the temperature in the compartment and operable to interrupt the supply of liquid refrigerant to the expansion valve periodically in accordance with changes of temperature in the compartment, a reservoir through which liquid refrigerant in said high pressure side passes to the expansion valve and which normally contains a supply of liquid refrigerant, a heater which is operable to heat the contents of the said reservoir, a control responsive to the pressure in the said high pressure portion to cause operation of said heater in the absence of said normally maintained sufficiently high pressure in said high pressure portion, means which is operable to isolate the contents of said reservoir from liquid refrigerant in said high pressure portion during the heating of the contents of the reservoir, and means controlled by the aforesaid thermostat to prevent operation of the heater during any period of interruption by said thermostat of the supply of liquid refrigerant to the expansion valve.

2. A refrigerating system in which a refrigerant is circulated and having a low pressure portion which includes an evaporator, an expansion valve through which liquid refrigerant is suppliable to the evaporator, and a high pressure portion from which liquid refrigerant issuppliable to the expansion valve and in which the pressure is normally maintained sufiiciently high to force liquid refrigerant through the expansion valve to the evaporator, and a pressure booster which is cooperable with said system and responsive to the pressure in the high pressure portion to temporarily isolate a portion of the liquid refrigerant in said high pressure portion in the absence of said normally maintained sufficiently high pressure in the high pressure portion, said pressure booster including heating means which is temporarily operable to independently heat said isolated portion of the liquid refrigerant and evaporate some of said isolated portion to produce a sufiiciently high pressure to force at least some of said isolated portion through the expansion valve to the evaporator, and means which is operable to discontinue such isolation and heating upon restoration of said normally maintained sufliciently high pressure in the high pressure portion.

3. A refrigerating system in which a refrigerant is circulated and subjected alternately to high and low pressures for liquification and evaporation thereof respectively for absorbing heat, the said system having alow pressure portion including an evaporator, a restrictor through which liquid refrigerant is supplied to the low pressure portion and the evaporator thereof, a high pressure portion which receives evaporated refrigerant from the low pressure portion and supplies liquid refrigerant through the restrictor to the low pressure portion, and main pressurizing means by which pressure is normally maintained in the high pressure portion sufiiciently higher than that in the low pressure portion to force liquid refrigerant from the high pressure portion through the restrictor to the low pressure portion, and facilities which are cooperable with the system to provide temporary supply of liquid refrigerant entirely to the low pressure portion in the absence of such normally maintained pres sure in the high pressure portion, the said facilities in cluding a control which is responsive to the pressure of the high pressure portion to cause the temporary supply to occur of liquidrefrigerant to the low pressure portion.

4. Refrigerating equipment comprising a circulation system comprising a series of passageways and parts through which a refrigerant is circulated and having a low pressure portion which :includes an evaporator. in

which the refrigerant is evaporated, a high pressure portion in which the refrigerant is compressed and liquefied, a compressor by which the evaporated refrigerant is evacuated from the low pressure portion and supplied to the high pressure portion at a pressure for conversion thereof to a liquid in the high pressure portion, and an expansion valve through which liquid refrigerant is suppliable from the high pressure portion to the evaporator by pressure of a predetermined amount normally maintained in the high pressure portion, and means for controlling the circulation of the refrigerant through said circulation system which said means includes instrumentalities which are responsive to the pressure in the low pressure portion to operate the compressor periodically to maintain a predetermined condition of evacuation in the low pressure portion, a compartment from which heat is extracted by the evaporator, instrumentalities which are responsive to the temperature in said compartment to supply liquid refrigerant periodically from the high pressure portion through the expansion valve to the evaporator and means which is responsive to the pressure in the high pressure portion and operable in the absence of normally maintained pressure of said predetermined amount therein, to provide temporary supply of liquid refrigerant entirely to the evaporator until normally maintained pressure of said predetermined amount is restored in the high pressure system, the said means including an auxiliary pressurizer which is temporarily operable in the absence of such normally maintained pressure to increase the pressure of an isolated part of the liquid refrigerant and force it through the expansion valve into the low pressure por tion of the system.

5. Refrigerating equipment comprising a circulation system comprising a series of passageways and parts through which a refrigerant is circulated and having a low pressure portion which includes an evaporator in which the refrigerant is evaporated, a high pressure portion in which the refrigerant is compressed and liquefied, a compressor by which the evaporated refrigerant is evacuated from the low pressure portion and supplied to the high pressure portion at a pressure for conversion thereof to a liquid in the high pressure portion, and an expansion valve through which liquid refrigerant is suppliable from the high pressure portion to the evaporator by pressure of a predetermined amount normally maintained in the high pressure portion, and means for controlling the circulation of the refrigerant through said circulation system which said means includes instrumentalities which are responsive to the pressure in the low pressure portion to operate the compressor periodically to maintain a predetermined condition of evacuation in the low pressure portion, a compartment from which heat is extracted by the evaporator, instrumentalities which are responsive to the temperature in said compartment to supply liquid refrigerant periodically from the high pressure portion through the expansion valve to the evaporator and means which is operable to supply liquid refrigerant temporarily to the evaporator, in the absence of the aforesaid normally maintained predetermined amount of pressure, and wherein the last mentioned means is readied for operation in response to the pressure in said high pressure portion and the time of operation thereof is determined by said instrumentalities, the said means including an auxiliary pressurizer which is temporarily operable in the absence of such normally maintained pressure to increase the pressure of an isolated part of the liquid refrigerant and entirely force it through the expansion valve into the low pressure portion of the system.

6. A method of refrigeration which comprises circulating a refrigerant through a system in which liquid refrigerant is evaporated in a low pressure portion of the system and transferred therefrom to and liquified in a high pressure portion of the system in which a sufficiently high pressure is normally maintained to return the liquefied refrigerant therefrom into the low pressure portion for evaporation therein, the said method including the occasional step initiated by and continued during absence of such normally maintained sufliciently high pressure in the high pressure portion of the system of isolating and temporarily subjecting a portion of the isolated liquid refrigerant to a high pressure by which it is forced entirely into the low pressure portion during such absence of such normally maintained sufficiently high pressure in the high pressure portion.

7. A method in accordance with claim 6 wherein the temporarily isolated portion of the liquid refrigerant is heated to produce the high pressure by which it is forced into the low pressure portion during the absence of normally maintained sufliciently high pressure in the high pressure portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,053,290 Kaufman Sept. 8, 1936 2,244,312 Newton June 3, 1941 2,359,595 Urban Oct. 3, 1944 2,367,306 Newton Jan. 16, 1945 2,453,131 Hubbard Nov. 9, 1948 2,459,173 McCloy Jan. 18, 1949 2,524,813 Lothrop Oct. 10, 1950 

